Development and Evaluation of Alternative Materials for Friction Stir Welding of Steel
Friction Stir Welding (FSW) was developed in 1991 at The Welding Institute (TWI) in Great Britain, and has become a widely used method of welding aluminium and copper structures. The method is based on a simultaneous application of pressure and friction which generates heat that leads to the softening of the join parts to be welded. Due to stirring the tool in the softened metal the connection of the components is ensured, as shown in Fig. 1. Besides the resulting high quality of the welds, FSW offers a multitude of advantages as the ability to join materials that are difficult to fusion weld, for example aluminium alloys, magnesium and copper as well as a good suitability for automation and adaptability for robot use. Due to low distortion and shrinkage even in long welds, excellent mechanical properties in fatigue, tensile and bend strengths can be achieved. In contrast to conventional processes, no arcs or fumes are produced, which is beneficial for health and environmental protection aspects. The welding process shows due to the lack of need for welding consumables and auxiliaries high potential for saving resources and energy. From an environmental point of view, it can be noted that FSW produces less waste in the form of slag, weld residue, pretreatment, etc., as compared to molten welding processes, and thus does not result in environmental stress from contained alloying elements, i.e. expensive recycling processes are not required [1, 2].